and many more benefits!

Find us on Facebook

GMAT Club Timer Informer

Hi GMATClubber!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Hi there folks,

I'm just beginning to prepare for the GMAT by using the Princeton Math Workout book (published 1998) and have a question that doesn't make sense to me.

Here it is,

How many positive integers less than 28 are prime numbers, odd multiples of 5, or the sum of a positive multiple of 2 and a positive multiple of 4.

(a)27
(b)25
(c)24
(d)22
(e)20

I put the answer and explanation, as well as my question further down in case you want to try to figure it out:

(d) is the correct answer. Here is the explanation for why:

The prime numbers are: 2,3,5,7,11,13,17,19,23 (total 9 )
The odd multiples of 25 are: 5,15,25 (total 3)
The numbers that can be expressed as the sum of a positive multiple of 2 and a postive multiple of four are all the even numbers over 4: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 (total 11)
grand total=9+3+11=23

So how can (d), which is 22, be the correct answer?

I apologize if I've overlooked a *really* obvious error--but I can't find it anywhere!

I'm just beginning to prepare for the GMAT by using the Princeton Math Workout book (published 1998) and have a question that doesn't make sense to me.

Here it is,

How many positive integers less than 28 are prime numbers, odd multiples of 5, or the sum of a positive multiple of 2 and a positive multiple of 4.

(a)27(b)25(c)24(d)22(e)20

I put the answer and explanation, as well as my question further down in case you want to try to figure it out:

(d) is the correct answer. Here is the explanation for why:

The prime numbers are: 2,3,5,7,11,13,17,19,23 (total 9 )The odd multiples of 25 are: 5,15,25 (total 3)The numbers that can be expressed as the sum of a positive multiple of 2 and a postive multiple of four are all the even numbers over 4: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 (total 11)grand total=9+3+11=23

So how can (d), which is 22, be the correct answer?

I apologize if I've overlooked a *really* obvious error--but I can't find it anywhere!

Any shedable light would be warmly received indeed,Marzipan

That's because 5 is common to both prime numbers and odd multiples of 5.